Inappropriate coronary vasomotion plays an important role in the pahtophysiology of myocardial ischemia, but mechanisms underlying coronary spasm are unclear, and methods of investigation are limited. The main objective of this application is to develop new receptor-pharmacological tools for the segment to segment evaluation of arteries with altered reactivity. Arteries are cut into serial transverse strips piled up to form a tissue block. The frozen tissue block is used to produce slide-mounted frozen sections displaying serial cross-sections of the vascular wall. Specific binding of radioligand to the sections after rapid wash are studied applying conventional criteria of receptor identification including saturability, kinetics of binding, stereospecificity, and tissue linearity. Data are plotted according to the Scatchard method for the determination of dissociation constants (KD) and maximal binding. Results are compared with those obtained with a conventional technique using arterial particulate fractions and removal of free ligand by vacuum filtration. Coincubated frozen tissue sections are used to generate autoradiographs for the localization of specifically displaceable 3H-ligand distributed across the arterial wall. The new 3H-ligand binding method is tested in aortas from normal and cholesterol-fed rabbits. The receptor-pharmacological properties of these arteries are assessed in organ bath studies. The KD of the ligands used for binding studies, all high affinity competitive antagonists, is estimated on the basis of the shifts of the dose-response curves for appropriate agonists (Schild plots). KD's for prazosin by the 3H-ligand procedures (homogenate or tissue section technique) and by the pharmacological procedure were in excellent agreement. The tissue section techniques are capable of yielding information about the affinity (1/KD) and distribution of receptor-specific ligands in biopsy-sized (20 mg) samples, and are applicable to fresh cadaver tissue. Therefore, the methods will be tested opportunistically in patients with coronary disease shortly after death.